The Victoria & Albert Museum ★★☆

The world's greatest museum of decorative arts—and so much more (this from someone who hates crafts museums)
I know you're getting tired of superlatives, but the V&A truly is the greatest museum of decorative arts in the world—the definition of "fascinating" for some, of "a lesser circle of Hell" for others.
Trust me, though, it's far, far, far more fascinating than it sounds. I am normally put to sleep by decorative arts museums, but I love this place.
Among my favorites parts: the Asian collections, the stained glass, the galleries of plaster cast reproductions of the world's most famous sculptures, the Samurai outfits, and the amazing musical instrument collection.
While interior decorating aficionados are enjoying 14th-century embroidery, Chinese vases, Indian furnishings, and historic British candlesticks, less enthusiastic companions can amuse themselves with the largest collection of Renaissance sculpture outside Italy (featuring Donatello, Rossellino, and Bernini), rooms filled with glorious artifacts from across Asia, and the Casts Courts (formerly known as the "Fakes and Forgeries" galleries) two high-ceilinged rooms packed with plaster casts of famous works of sculpture from around the world and throughout history.
A favorite: The Raphael Cartoons, seven large paintings by Raphael that where the models for a series of tapestries commissioned by Pope Leo X to hang in the Sistine Chapel (they have since been moved to the Vatican Museums' painting gallery). Carefully rendered so they could be faithfully reproduced by the Belgian weavers on their looms, and painted with glue distemper on paper, the cartoons were acquired by King Charles I in 1623. For centuries they were the pride of Hampton Court Palace; Queen Victoria had them moved here in 1865.
Tips
I'd budget a bare minimum of an hour at the Victoria and Albert Museum. It's huge, and it sprawls, and it's tough to find all the interesting nooks and crannies.
Two hours would be a wiser choice.